In the manufacturing process of, for example, a liquid crystal display or a semiconductor device, a circuit pattern is formed on a substrate such as a glass substrate having a rectangular shape or a semiconductor wafer (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2010-010555). When a circuit pattern is formed, development and an etching process of a substrate and peeling of a resist are performed by a substrate treating device. A treatment liquid used to treat a substrate is prepared and stored in a feeding tank of a liquid feeding device to feed the treatment liquid to the substrate when needed. Such a treatment liquid is expensive and so is returned to the feeding tank again after being separated and recovered.
For example, two feeding tanks are provided to a liquid feeding device and one tank is used at a time. The treatment liquid in the feeding tank not in use is periodically circulated by a pump. Because the treatment liquid is degraded with the passage of time or with use, a life time is set and the treatment liquid is disposed of when degraded.
The feeding tank is provided with an exhaust passage in an upper portion thereof and an overflow line on the side thereof and these passages are open. The exhaust passage is provided to prevent a negative pressure inside the feeding tank when a treatment liquid is fed from the feeding tank to a substrate by a pump and the overflow line is provided to prevent a treatment liquid inside the feeding tank from exceeding a fixed liquid level.